\section{Preliminary Experiment Using An Existing Game} \label{preliminaryTest}
Before diving deeper into the field of haptics, it's important to investigate whether it is even feasible to use controller vibrations as a way to deliver asymmetric information. I.e.\ whether players notice their peers' vibrations at all or not. If the vibrations are too apparent for the players, the project might need to take a different approach. Therefore, a preliminary test was conducted to measure how the controller vibrations were perceived in an existing multiplayer game with four players.

It is important that the vibrations provide information that is as hidden as possible to other players. In other words, if player A's controller vibrates, players B, C and D should not know about it. Obviously, it is possible to look down at player A's controller and see if it is vibrating, but since everybody is playing a game on the screen, this is not feasible, because the main focus is on the action displayed on the screen. Another aspect is the sound emitted from the controller when it vibrates. Being in a room of total silence, it is possible to hear the vibrations. But again, this is not the case, since the context is playing a multiplayer game with four people, presumably chatting or maybe even shouting at each other.

The preliminary experiment was conducted using \textit{Hidden in Plain Sight}, which is a local multiplayer game about deception. Four test participants played the game, each with their own Xbox 360 controller, for approximately one hour. \textit{Hidden in Plain Sight} is a game where the goal is to deceive the other players by blending in with a crowd of computer-controlled characters (see Figure \ref{fig:hips}). The game is relatively slow-paced, but still provides multiple game mechanics and tactics. The game takes place on a single screen where everything is publicly visible, but since all of the characters look the same, it is possible to hide oneself by moving in a certain pattern that simulates how computer-controlled characters move, e.g.\ casually walking back and forth instead of running around in circles.

\begin{figure}[htbp]
\centering
\includegraphics[width=0.60\textwidth]{Pictures/Design/hiddenInPlainSight}
\caption{In \textit{Hidden in Plain Sight}, each player controls a ninja. However, computer-controlled ninjas also walk around, making it possible to blend in with the crowd. The goal is to figure out who the other players are by looking at their behaviours in the game. \citep{hips_image}.}
\label{fig:hips}
\end{figure}

The test participants played the game as intended from the original developer. The only difference was a simple program running in the background on the computer. At randomly-chosen intervals ranging from 5 to 90 seconds, controllers would start vibrating with intensities ranging from full power to little power, and for a randomly-chosen time duration ranging from 0.1 to 2.5 seconds. To get an initial understanding of how players react to the vibrations, relatively big values were chosen for the vibration durations and power. Obviously, \textit{Hidden in Plain Sight} isn't designed with these vibrations in mind, which is why it was deemed better to have high values for this initial experiment and then tone them down in future experiments, if necessary.

Every time a player perceived a vibration, be it from his own controller or another player's controller, he was supposed to press a button to indicate that he noticed the vibration. To make everything as simple as possible, the participants only needed to press a single button whenever they perceived any vibrations. It didn't matter whether it was their own controller vibrating or the persons' sitting next to them; the button to press remained the same.

Each time somebody pressed their button, it was logged in a text file on the computer (see Appendix A).

Through the preliminary experiment, it was found that players seldom noticed when other players' controllers vibrated. Only a few times did the test participants take notice, and when they did, this often happened close to the beginning of the game. After the experiment, the participants were asked if they noticed their peers' controllers vibrating. The consensus was that they barely detected them at all.

Another thing that was discovered was that the test participants sometimes didn't notice vibrations in their own controller. Even though the gameplay didn't utilize the vibration in any meaningful way, it is a problem that needs to be dealt with. It is possible that they didn't notice the vibrations due to the fact that their focus was on the game itself which didn't use the vibrations.

It should be pointed out that the vibrations happened randomly, i.e.\ players didn't have any influence as to when their controller started vibrating. An idea would be to let the vibrations become "on-demand", so players can activate them at will. This might solve the problem of players not noticing their own vibrations.

\label{Hips}